[ICOM] 706 MK2G Finals - possible replacements?

[Dan Doss]

Hello all,

First off let me say that I'm relatively new to the reflector so please 
excuse any redundancies in what follows on the subject. That being said - 
I, like many on the reflector, have had to replace the HF finals on the 
706. The last time I did, the original SRFJ7044 MosFET's were available 
from Icom, albeit at a premium price. A call to Icom yesterday brought me 
aware of the fact that these transistors are available only for repairs 
made by Icom services centers. This fact may already be known by many, but 
was a little disconcerting to me. I was told that the only way one (an 
individual) could repair their blown finals was to buy a complete new PA 
assembly. I was given a part number of 98414684 (which is available) and 
lists for $293.33. Yikes! I was also told that the finals used on the new 
PA assy were not "compatible" with the older boards. When asked if this was 
due to electrical or physical reasons, the nice parts lady indicated that 
she thought is was because of physical differences. This was not confirmed 
by an Icom tech.

After a bit of research, I found that the SRFJ7044 MosFET is packaged in 
what Motorola/Freescale/MA-Com calls "Case 316-01". This is a 6-legged 
package with is attached to the heatsink with two screws. Other similar 
MosFET's (such as MRF150) use a stud-mount style package. I have not seen 
what transistors are used on the new style PA. There may very well be both 
physical and electrical differences between the two parts. Without having 
data sheets on either, it's difficult to ascertain if an off-the-shelf (and 
still in production) replacement part exists. I seriously doubt that Icom 
would be the least bit interested in locating such a device.

Not to be too long winded about the subject, but at a repair cost of nearly 
$300, it might be worth it to the group if we could attempt to locate 
another non Icom-specific part to repair our rigs with. If anyone has 
access to a network analyzer (and a spare '7044), it should be possible to 
characterize the old part so that a potential replacement could be 
researched. A quick search on MA-Com's website yielded a couple of 
transistors of the same power class and package that _might_ have similar 
characteristics (s-parameters, etc) to the '7044. I would be willing to use 
my 706 as a "test bed" for the cause if we can get some specs on the old part.

Let me also say that I am not in the business of repairing radios for hire. 
I just hope to spark some interest so that we might be able to keep our 
venerable 706's running without having to break the bank for repairs or as 
might be hoped by some, buying new rigs...

Any thoughts???

73,
Dan - KG0MM